In recent years electrophotographic copiers that are capable of automatically producing multiple collated sets of copies of a multiple-page original have been developed. Such copiers typically operate by circulating originals from a stack past an exposure window, one sheet after another, for a number of passes equal to the number of sets of copies to be made.
One of the problems of copiers of this type, which are designed and used to produce a large number of copy sheets without human intervention, is the design of the copy exit tray. If one assumes a typical sheet thickness of 0.1 millimeter, then an exit tray capable of holding 800 sheets, for example, must be positioned at least 8 centimeters below the final set of exit rollers to allow the last sheet to clear the top of the stack. However, a drop of this distance results in unreliable stacking, owing to the size of the air pocket between the top of the stack and the sheet being fed. Rather than falling directly on the stack, the sheets tend to float down, thereby becoming misaligned. This misalignment is especially troublesome in copiers that stagger alternate sets of copy sheets to facilitate their ready separation.